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TAPS construction required innovations Permafrost was first challenge for line; Denali Fault section, designed to move vertically and laterally, withstood 2002 quake Tim Bradner For Petroleum News
Construction of the trans-Alaska pipeline system, TAPS, was an engineering and technical marvel, but it was also a challenge where oil companies and pipeline builders had to learn fast, adapting as they went.
Pipeline engineers understood how to build across central Texas or in Nebraska, but they didn’t understand, at first, that the Arctic was different.
The first big unknown the industry confronted was permafrost. Mainly, the pipeline planners, at first, didn’t understand permafrost, the permanently frozen soil that lies just a few feet below the ground surface.
The initial estimate of the cost of TAPS, mentioned in a press conference in 1969 in Anchorage, was $900 million. The estimate was put together in Houston by engineers who assumed the 800-mile pipeline could be buried its entire length, as if it were in Nebraska.
When pipeline planners actually came to Alaska they learned about permafrost. It was a rude awakening.
The University of Alaska hosted a major Arctic science conference in Fairbanks in 1969 that was attended by scientists familiar with the Arctic, Alaska engineers with experience and industry officials. Conservation groups were also there, taking notes on the weaknesses in the early pipeline plans and preparing for lawsuits.
The National Environmental Policy Act had just become law on the federal level, and TAPS was to be the first major test of the new law. It guaranteed a thorough technical review by government scientists who, at the time, knew more about the Arctic than did the industry.
Alaskans knew a lot about permafrost, of course. Walt Phillips, a permafrost scientist, said great deal of experience had been gained at the university as scientists there helped gold mining companies deal with unstable soil. Also, state highway engineers designing roads and bridges had to deal with it, he said.
Individual oil companies exploring the North Slope had also learned hard lessons early. Roger Herrera, a retired BP geologist, said that company’s first effort to drill an exploration well on the Slope, in summer, resulted in a mess.
BP learned quickly and hired Nabors Drilling, an experienced Canadian contractor, who showed BP that exploration should be done in winter.
Phillips said what really alerted the pipeline engineers planning TAPS to permafrost, however, was the furor that developed over the Hickel Highway, an ill-advised attempt by the state of Alaska to truck supplies to the North Slope through Anaktuvuk Pass and across the unprotected tundra. The resulting landscape scars were an embarrassment, and although the Hickel Highway was a state project the publicity, and aerial photographs of damaged tundra, gave environmental groups new ammunition.
Pipeliners were fast learners All this was new to the pipeline planners, but they were fast learners. Dr. Hal Peyton, head of the University of Alaska’s School of Engineering, as well as research geologist Ralph Migliaccio, dissuaded the companies from the notion that TAPS could be buried its entire length. Peyton and Migliaccio explained that a hot oil pipeline in permafrost would create massive melting.
University scientists, including Peyton, Migliaccio and others and state highway engineers and geologists who knew about permafrost, were ultimately hired to help Alyeska Pipeline Service Co., then newly formed to manage construction of TAPS, design the project so that it would be safe.
Also lending expertise were Dr. Max Brewer and his staff at the Naval Arctic Research Laboratory at Barrow. Peyton eventually became engineering manager for the giant project.
As more was learned about ice-rich soils it was decided that about half of the pipeline’s 800-mile length would be built aboveground, on steel support structures with newly invented passive refrigeration to chill soils at critical spots. A pipeline built above ground, at that scale, had never been done before. Nor had passive refrigeration been installed at that scale.
Dave Norton, with Hawk Consultants, worked on TAPS engineering during its construction and recalls that much of the concept development of the aboveground and passive refrigeration was done by Exxon.
All of this happened as Alyeska and its engineers gained more knowledge of the actual soils they faced in building TAPS, and this didn’t come until the companies were able to get into the field to do geotechnical drilling.
The cost of the pipeline also began rising, from $900 million to $2 billion, and then $4 billion and $5 billion. It was eventually to reach $10 billion, although part of that, perhaps as much as half, was caused by inflationary pressures on wage, material and supply costs. The 1974 Arab oil embargo happened just as construction of TAPS finally started, and the project quickly became an urgent national priority to assure domestic oil supplies.
Denali Fault and the 2002 quake Meanwhile, one bit of innovative engineering for TAPS turned out to be critical. Tom Krzewinski, a geotechnical engineering consultant now with Golder & Associates in Anchorage, helped with field investigations in support of TAPS design teams.
The teams developed a special design for the Denali Fault in the Alaska Range. “People still remembered the 1964 Alaska earthquake and the pipeline engineers were very conservative with their design, particularly at a 300-foot section where the Denali fault is crossed,” Krzewinski recalls.
The above ground design allowed the pipe to move vertically as well as laterally on horizontal Teflon coated beams. Initially the design for the Denali fault allowed 20 feet of horizontal movement and 3 feet of vertical movement, but as an added precaution this was changed to 5 feet vertical and wider allowance for horizontal movement, Krzewinski said.
When a magnitude 7.9 earthquake hit along the Denali Fault on Nov. 2, 2002, the pipeline was severely jolted, but it never fell off its supports or ruptured. “The design was spot-on. The fault itself moved approximately 18 feet horizontally with 2.5 feet of movement vertically,” Krzewinski said
It was a strong testimonial to the engineers who developed the design, which passed a severe test. Nothing like it had been done before.
Norton has an interesting anecdote about the Denali Fault design. In 2002 TAPS was in the middle of securing a renewal of its federal right-of-way lease. Norton and others at Alyeska were working with the U.S. Bureau of Land Management on the renewal.
Just prior to the earthquake, BLM had signed off on accepting the technical performance of most of the original TAPS engineering and construction. After 30 years, they had proved the effectiveness and safety of the design and BLM accepted them, Norton recalled.
The exception was the seismic design standards. There hadn’t been an earthquake so the design wasn’t “proven.” It had become a major issue for the right-of-way renewal.
Then the earthquake happened. The 1970s-era design proved itself.
“We didn’t hear a word about it after the earthquake,” Norton recalls.
Mile 200 incident One incident that was a real wake-up call for Alyeska, however, was an unexpected settlement of buried pipe in 1984 at a stream crossing near the Dietrich River 200 miles south of Prudhoe Bay, Norton said. An undetected permafrost lens below the river had melted, causing the pipe to settle about 14 feet to 15 feet.
That was enough to be a serious concern. “There was enough stress on the pipe that we couldn’t understand why it didn’t rupture,” he said.
Had that happened it would have been a major oil spill and in an estuary at that, a dire confirmation of environmentalists’ worst predictions.
Fortunately the pipe deformation was detected, a rerouting quickly accomplished, and the issue was resolved. Norton is proud of the way Alyeska responded because it was the first near-emergency situation the pipeline company confronted.
“We were seven years after startup and things had been going very smoothly. The operation has settled into a normal routine and there was almost a complacency that had set in, and even the kind of minor internal disputes and rivalries that happen in organization,” Norton remembered.
“But when this happened it was suddenly ‘all hands on deck,’ and it was amazing how quickly and effectively the organization pulled together. I was quite proud to be part of it,” he said.
Post-construction innovations There were examples of technical innovations driven by TAPS that came after construction, too. One was the evolution of “smart” pigs for pipeline internal inspection, Norton said.
Pigs, or mechanical devices that are put through pipelines for maintenance, have long been used in the pipeline industry, but for TAPS government regulators demanded a system that would ensure the integrity of the pipe against corrosion.
Alyeska’s response was development of the “smart” pig, a device with instruments to detect loss of pipe wall thickness, or bending. “The Japanese developed it, and this was the first time something like this had been done,” Norton said.
Yet another innovation was the first use of drag-reducing agent, a chemical injected into the crude oil to enhance the flow through the pipe.
The so-called DRA wasn’t needed after decline began in the North Slope fields in 1988 and the TAPS throughput began dropping, but use of the chemical allowed Alyeska to actually exceed TAPS’ 2 million barrel-a-day design capacity for a period. For a while TAPS actually moved 2.1 million barrels per day.
Norton recalls that the DRA also allowed Alyeska to scale back on pump capacity at two pump stations and to eliminate construction of one that was in the original plan. DRA allowed more oil to be flowed with less pump capacity, so it saved on capital costs.
Recirculation of heat Alyeska’s current practice of recirculating oil through pump station pipe loops to add friction, and heat, was another innovation by the pipeline’s engineers, this one caused by another near emergency.
The problem was that a small leak at Pump Station One, at Prudhoe Bay, had caused a shutdown of TAPS in the middle of winter while the leak was repaired.
The pipeline was idled for several days during which the crude oil gradually cooled. Alyeska’s operators became seriously concerned that there would be difficulty restarting TAPS with its cold oil. Fortunately the pipeline was restarted and operations returned to normal but during those tense days Alyeska’s engineers were brainstorming ways to keep the oil warm during winter. An inspiration, subsequently put into practice, was to recirculate the oil to add heat.
The procedure is now a normal part of TAPS’ winter operations, and the extra heat is a safety margin in case of another winter shutdown.
Atigun Pass One of the most interesting stories from the earliest days of planning for TAPS was the routing of the pipeline through the Brooks Range. In the beginning, the pipeline planners didn’t know about Atigun Pass.
It was thanks, indirectly, to the wolf hunters of Fairbanks that early planners for the pipeline found Atigun Pass.
When the first pipeline team arrived in Fairbanks in 1969 they didn’t know about Atigun. They were focused on Anaktuvuk Pass as a route for the pipeline.
“People in Fairbanks knew there was a pass farther east than Anaktuvuk but the wolf hunters, who flew up there all the time, knew where it was,” recalls Terry Brady, a Fairbanks resident then working with the University of Alaska.
Maps at the time were poorly marked and Atigun wasn’t identified. Brady recalls talking about the eastern pass while accompanying the team to Barrow to discuss permafrost with Max Brewer, then-director of the Naval Arctic Research Laboratory.
Brewer reaffirmed the existence of Atigun and showed the team where it was on maps. With Brady along, the group flew east and then south along the Sagavanirktok and Atigun Rivers.
Atigun is higher, and steeper, than Anaktuvuk. “As we circled the pipeline people looked down and wondered how anything could be built through there,” Brady remembers. “They thought a tunnel would be the only way.”
But build they did. Atigun was selected mainly because the route would be shorter, although more difficult, than a route via Anaktuvuk. TAPS had to cross three mountain ranges along its 800-mile route, and building through Atigun and Thompson Pass, north of Valdez, presented formidable challenges.
The job was all difficult, and all a challenge. But it got done.
Tim Bradner is copublisher of the Alaska Legislative Digest and editor of Alaska Inc., a quarterly magazine
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